Fix white screen after login: pushReplacement to DashboardScreen; main decides home by email presence; add missing imports

lib/main.dart

@@ -30,6 +30,7 @@ class MyApp extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final theme = Provider.of<ThemeProvider>(context);
+    final auth = Provider.of<AuthService>(context, listen: false);
     return MaterialApp(
       title: 'Login Vault',
       theme: ThemeData(
@@ -43,13 +44,10 @@ class MyApp extends StatelessWidget {
         colorSchemeSeed: Colors.indigo,
       ),
       themeMode: theme.mode,
-      home: registered
-          ? DashboardScreen(
-              auth: context.read<AuthService>(),
-              theme: theme,
-              email: email,
-            )
-          : AuthScreen(auth: context.read<AuthService>()),
+      // decide home: if registered AND email known -> Dashboard, else Auth.
+      home: (registered && email.isNotEmpty)
+          ? DashboardScreen(auth: auth, theme: theme, email: email)
+          : AuthScreen(auth: auth),
       debugShowCheckedModeBanner: false,
     );
   }